We also surveyed a Bosch UL-S package boiler with a radiometric camera. Every surface it has carries its own measured page — FLIR temperature, area, ISO 12241 heat loss.
A ZFR running at 6–10 bar sits at a saturation temperature around 165–185 °C. The shell is clad from the factory; what is not clad is everything that has to open or move — the front door, the burner flange, the inspection hatch, the safety valves, and the frame that carries them.
Those five groups add to 53.4 kW of continuous loss. With removable panels the same set holds 4.0 kW, a 92.5 % cut, with every outer sursurface at or below 45 °C.
The door alone is 32.9 kW — 62 % of the whole figure. It is also the single surface most often left bare, because a fixed box over a boiler door is a box that gets cut off at the first tube inspection.
Model inputs: ISO 12241 steady state, ambient 25 °C, 50 mm mineral-wool core, ε 0.9 on bare steel. Element areas from the CAD model; loss per element scaled from the reference heat-loss study for this boiler class (×1.78 for the surveyed set). Fuel from heat via 85 % boiler efficiency.
| Element | Qty | Bare | Share |
|---|---|---|---|
| Front door | 1 | 32.9 kW | 62 % |
| Burner flange | 1 | 11.0 kW | 21 % |
| Metal frame | 4 | 4.9 kW | 9 % |
| Safety valves | 2 | 3.0 kW | 6 % |
| Inspection hatch | 1 | 1.5 kW | 3 % |
| Bare, per boiler | 9 | 53.4 kW | 100 % |
| With Inzonex panelss | — | 3.99 kW | 7.5 % |
Measured on the Bosch UL-S: a radiometric FLIR survey recorded 190 °C on bare steam valves, 146 °C on the burner flange and 96 °C on the door — falling to 36, 30 and 30 °C once panelled. See the measured case →
Every one of these surfaces is opened on a schedule. What changes with the panel is not whether it opens — it is what opening costs.
| Conventional cladding, per access | |
|---|---|
| Unscrew or cut the sheet panels | |
| Dig out the wool — settled and degraded by heat and vibration | |
| Rebuild the wool, cut and fasten new sheet | |
| Cycle per access | 10+ min* |
| Inzonex cycle, per access | |
|---|---|
| Release the snap buttons by hand — no tools | |
| Lift the section clear | |
| Snap the same section back | |
| Cycle per access | ~1.5 min* |
*Access-cycle assumptions, not timed trial results — treat them as inputs to check against your own crew, not as measured performance. Cut sheet and compacted wool are scrapped, so conventional access also carries a material cost every time. The panel is designed to come off and go back on; nothing is consumed.
A sheet-metal casing has to span every surface these panels span. Same job, same surfaces — the difference is what a technician lifts.
| Outer layer, whole set | Weight | Basis |
|---|---|---|
| Steel sheet 0.6 mm lightest gauge used | 128 kg | 7850 kg/m³ + Z275 zinc |
| Steel sheet 0.8 mm common on plant — basis | 170 kg | same, 0.8 mm |
| Steel sheet 1.0 mm walked-on / wind-loaded runs | 213 kg | same, 1.0 mm |
| Inzonex outer fabric | 14.3 kg | our spec |
About 12× lighter on the 0.8 mm basis. The mineral-wool core is identical in both systems — it is the outer layer, and only the outer layer, that the design can change. That is what a technician lifts, at height, next to a live boiler.
Heat lost from a bare surface does not leave the building. It goes into the plant-room air, every hour the boiler runs. On this set that is 49.4 kW — the difference between 53.4 bare and 4.0 insulated — delivered continuously into a room nobody is trying to heat. Sixteen three-kilowatt fan heaters, never switched off.
That load has three costs, and only the first shows up on the gas bill:
| Consequence | What it looks like |
|---|---|
| Fuel | The boiler regenerates the heat it just threw away. |
| Working conditions | Plant-room air climbs; in summer the room becomes somewhere work gets rushed or deferred. |
| Contact burns | Surfaces at 96–190 °C at working height, next to the valves an operator reaches for. |
ISO 13732-1 sets the contact-burn thresholds for hot surfaces. Bare steel at 100 °C burns on contact in about a second; at 190 °C it is immediate. Insulated to ≤45 °C the same surface can be held indefinitely — which is the point of specifying the outer surface temperature rather than only the saving.
On the radiometric survey of the UL-S, 35 of 38 infrared frames showed exposed metal above 60 °C, and the plant room measured around 6 °C cooler once the bare components were panelled. The measured case → Room temperature depends on ventilation and building fabric, so treat the direction as transferable and the magnitude as site-specific.
| Bosch UL-S surface | Bare | Panelled | Cut |
|---|---|---|---|
| Steam valves | 190 °C | 36 °C | 93 % |
| Burner flange | 146 °C | 30 °C | 96 % |
| Boiler door | 96 °C | 30 °C | 93 % |
| Whole UL-S | 23.4 kW | 1.2 kW | 94.9 % |
FLIR S62 Pro, 38 radiometric measurements, recomputed per pixel from the raw thermal matrix and checked against the ASTM C680 / ISO 12241 model. That survey panels a smaller 6-ton boiler than the ZFR modelled above — the temperatures transfer, the kilowatts do not.
Same camera, same settings, same three locations — the whole point of a radiometric survey is that the second visit is comparable to the first.
7,700 h/yr is near-continuous process duty. Move the slider to your own hours.
The part a heat-loss calculator normally leaves out. Count every time a panel has to come off — inspection, valve work, cleaning — not the number of boiler shutdowns. Cycle times are project assumptions; overwrite them with your own.
Carbon price left at zero unless your site is inside a trading scheme or has an internal price. UK ETS and EU ETS both apply to installations above the combustion threshold — carbon hub →
CAD reconstruction and thermal modelling by the Inzonex engineering team. The 3D models behind these comparisons are built by hand from field-surveyed equipment, not from manufacturer artwork.